Method of determining the presence of an unconsolidated plug



Jan. 20, 1970 Q o. G. MGQCLAIN 3,490,528

METHOD OF DETERMINING THE PRESENCE OF AN UNCONSOLIDATED PLUG Filed Jan.12, 1968 Fig. it "f 40 70 I I QQKW XKAW- M/AW/A ki/AW/XZ Orville 6. MaC/ain IN VEN TOR.

United States Patent US. Cl. 166-253 1 Claim ABSTRACT OF THE DISCLOSUREA well tool for determining the presence and position of a plugestablished by plug forming material in a well bore, generally prior tohardening of the plug forming material. which tool comprises a shoeplate means adapted to be removably secured to the lower end of a pipestring and including a relatively large diameter disk-like plate normalto the longitudinal axis of the pipe string and wherein the plate isfreely slidable within the well bore but has a radial cross-sectionalarea greatly in excess of the radial cross-sectional area of the pipestring whereby the effective force exerted per unit area of lowersurface of the pipe string can be substantially reduced to permit thepipe string with the tagging shoe attached thereto to be supported byplugging material within the bore of a well whereby the presence of adownhole plug may be determined from the well head prior to setting ofan initially fluent plugging material.

The present invention relates to a well plug tagging method and means.More particularly, the present invention relates to the provision of awell plug tagging shoe to be utilized in a well cementing procedure todetermine the presence of a well bore plug formed by a generallycementitious material introduced into a well bore. More specifically,the present invention relates to a well plug tagging shoe which may beremovably coupled to the lowermost connector of a pipe string.

In the setting of cementitious well bore-occluding plugs in wellsdrilled, primarily for gas and oil, but not necessarily excluding water,it frequently is necessary to prove the existence or effectiveness ofsuch plugs by tagging them. The usual practice has been to cement theplug i.e., introduce the cementitious material into the bore hole, witha string of pipe that is open-ended In such a case the cross-sectionalarea bearing upon the cementitious material is small, being thecross-sectional area of the pipe, and the cementitious material must beallowed to harden to a great degree before it is sufficiently competentto bear the static weight of the pipe string without permitting thestring to pass downwardly therein which occurrence is highly undesirableinasmuch as it adversely effects the plug being established and alsodoes not permit the accurate determination of the existence and positionof the cementitious plug.

Accordingly, it is a primary object of the present invention to providea well tool, i.e., tagging shoe, for rapidly and accurately determiningthe presence and position of a well plug established by plug-formingmaterial in a well bore generally prior to final hardening of theplugforming material.

Another object of the present invention is to provide a novel method ofrapidly and accurately determining the presence and position of a wellplug established by plugforming material introduced into a well borewherein removably secured shoe plate means is provided for substantiallyincreasing the contact area of the lowermost end portion of a pipestring whereby generally cementitious plug-forming material within thewell bore can be 3,490,528 Patented Jan. 20, 1970 tagged at a muchearlier stage in the process of its setting or hardening wherebysignificant economies of operation will be realized due to a reductionin the time required to satisfactorily complete the plugging of wellsdrilled for gas, oil and water.

Still another object of the present invention is to pro vide a novelconstruction for a well plug tagging shoe having a generally tubularbody portion provided with coupling means to be removably secured to thelowermost pin or box connector portion of a drill pipe string or thelike and wherein the body portion is provided with a generally disk-likeshoe plate of substantially greater radial crosssectional area than thelower end of the pipe string and wherein the major axis of the shoeplate is generally normal to the longitudinal axis of the pipe string towhich the tagging shoe is secured.

Still a further object of the present invention is to provide a wellplug tagging shoe of the aforementioned general construction wherein thetubular body portion and/or the shoe plate are provided with a pluralityof circulation or relief ports to permit the circulation of fluid duringutilization of the tool, if desired, and to generally preclude floatingof the tagging shoe on relatively nonviscous fluid within a well boreabove a portion of generally cementitious or plastic plugging materialwithin the well bore to be tagged by the tool.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter de scribed and claimed, referencebeing bad to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a longitudinal cross-sectional view through a plugged wellbore further showing an exemplary embodiment of a tagging shoeconstructed in accordance with the present invention and removablysecured to the lowermost section of a pipe string as utilized in themethod of the present invention;

FIGURE 2 is an enlarged longitudinal cross-sectional View of theexemplary tagging shoe of FIGURE 1 taken substantially along the planeof the line 2-2 of FIGURE 1 and showing circulation or relief portdetails thereof;

FIGURE 3 is a transverse, or radial, cross-sectional view takensubstantially along the plane of the line 33 of FIGURE 2; and

FIGURE 4 is a perspective view ofthe exemplary tagging shoe of thepreceding figures.

Briefly, the method of the present invention for the rapid, accuratedetermination of the presence and position of a generally cementitiousWell plug forming body of material within a well bore utilizes a wellplug tagging shoe provided with a load bearing surface substantiallylarger in area than normally provided by the lowermost portion of a pipestring whereby a shoe plate provided on the lower end of the welltagging shoe, and having its major axis generally normal to thelongitudinal axis of the pipe string and thus also the well bore,reduces the effective static weight of the pipe string by substantiallyreducing the effective weight per unit area of the string whereby thematerial utilized to establish the plug may be tested for the presenceand position thereof by the tagging shoe before the material hassubstantially hardened.

Referring now in greater detail to the drawings, and FIGURE 4 inparticular, it will be seen that the exe1nplary embodiment 10 of a wellplug tagging shoe constructed in accordance with the invention includesa generally tubular tool body portion 14 having a fluid passage definingbore 16 extending longitudinally therein. The upper portion of the tool'body 14 is provided with a coupling means 18, which in the embodimentillustrated, comprises the threaded box portion of a threaded pin andbox connector means conventionally utilized in well apparatuses. In thisregard, and as best seen in FIG- URE 2, the well plug tagging shoe isillustrated as operatively positioned on the lower end portion of a pipestring section having a threaded pin coupling means 22 complementary tothe threaded box 18 whereby the tagging shoe 10 can be removably securedto the pipe string section 20 with the fluid passage defining bore 16 incommunication with a fluid circulating bore 24 as conventionallyprovided in well pipe strings.

A shoe plate means 26 is fixedly secured to or otherwise rigidly affixedto the lower end portion of the tool body 14. which securement in theembodiment illustrated comprises an annular well bead indicatedgenerally 28 and a bracing means comprising a plurality of bracinggussets 30 secured to both the body portion 14 and the shoe plate 32 soas to further rigidify the securement of the tagging shoe means 26 tothe body portion 14. The bracing gussets 30 may be secured in therelationship illustrated by welding. It will be understood that themanner in which the shoe plate 32 is secured to the body portion 14 ismerely exemplary and does not preclude, for example, securing the shoeplate 32 to the body portion 14 by other suitable means such asfasteners, a threaded coupling, as long as the securement is relativelyrigid. Furthermore, it will also be understood that the threaded boxconnector portion 18 is merely exemplary of a plurality of conventionalconnector means which can be utilized in securing the well plug taggingshoe 10 to the lower end of a pipe string or the like. Still further, itWill be appreciated that the length of the body portion 14 illustratedis merely exemplary.

The well plug tagging shoe 10 may further include a fluid circulationport means comprising one or more through apertures in the body portion14 and/or the shoe plate 32 which through apertures place the bore 16 indirect communication with the exterior of the body portion 14, and thusthe well annulus thereabout above the shoe plate 32 and/or alternativelyplace the bore 16 in direct communication with the underside of the shoeplate 32. Circulation ports as discussed hereinabove are indicatedgenerally at 34 and 36 respectively. In addition, the tagging shoe plate32 may be provided with one or more through apertures as indicated at 38which place the upper and lower surfaces of the tagging shoe 32 indirect communication to permit circulation of relatively non-viscousfluid as indicated at 40 within the annulus defined by the bore wall 42,or alternatively a casing, not shown, so as to generally permitunimpeded movement of the well plug tagging shoe 10 downwardly andupwardly within the fluid 40 containing bore. It will be understood, ofcourse, that when providing the tagging shoe plate 32 with circulationports as at 36 and 38 that the amount of material removed by such portswill in part be limited by the total bearing surface area of theunderside of the tagging shoe plate 32 which is required to support thecomplete or partial weight of the pipe string to which the tool 10 isoperatively secured.

With further regard to the tagging shoe plate 32, and inasmuch as theshoe is adapted to substantially reduce the force exerted by the pipestring per unit of surface area, the tagging shoe plate 32, which is ofa generally disk-like configuration, is normally devised so as to have agreat radius as is possible, which radius is always substantially largerthan the radius of the lower end of the pipe string, but of somewhatsmaller radius than that of the bore hole or casing within which thetool 10 is utilized. Furthermore, it will be appreciated that thecircular disk-like configuration of the shoe plate 32 illustrated ismerely exemplary in that the plate 32 could be of numerousconfigurations, i.e., convex, concave, wedgeshaped and need notnecessarily have circulation ports therein or alternatively the shoeplate 32 may be provided with a back pressure valve, such as in theaperture 36, so that fluid could pass downwardly through the valve yetno fluid could pass upwardly through this valve as the tool is loweredinto the hole.

With further regard to the bracing gussets 30, they serve as combinationbrace and tool guide means inasmuch as very often the tagging shoe 10will be run through well casing adjacent the ground surface to tag aplug in a portion of the bore hole which has been drilled to a depthbelow that of the lower end of the well casing. Therefore, whenutilizing the tagging shoe 10 under such conditions, as the tagging shoe10 is withdrawn from the bore hole, there is the possibility of ithanging up on the bottom of the casing. In fact, other bore holeobstructions can be encountered, i.e., sidetracked pieces of pipe, metalobjects that occasionally fall into the bore hole and are subsequentlydrilled past but continue to protrude into the bore hole, pieces offormation rock that heave out into the bore hole, etc. It will thereforebe appreciated that the gussets 30, which generally extend from theupper peripheral edge of the shoe plate 32 to the outer surface of thebody member 14, are generally of such configuration that they provide asloping cam surface to facilitate guiding the tagging shoe 10 past orthrough obstructions such as mentioned hereinabove. In addition it willbe appreciated that by rotation of a tool string to which the taggingshoe 10 is removably secured, many of such obstructions could begradually broken up and subsequently washed away.

Referring now to the utilization of the well plug tagging shoe 10 andthe instant method of accurately determining the presence and positionof a plug within a well by utilization of the tool 10, it will be seenin FIG- URES 1 and 2 that the tool 10 has been aifixed to the lowermostsection of pipe 20 which comprises a portion of a pipe string extendingto the well head. In FIGURE 1 it will further be seen that the lowerportion of the bore 42 has been filled with a generally settable plugforming material 44 such as comprising a cementitious composition oralternatively a resinous composition and for that matter any solid,semi-solid or extremely viscous material that has been placed in a borehole or casing and whose presence it is desired to verify by resting anyor all of the weight of a pipe string upon it. For purposes ofdiscussion herein the plug material 44 is illustrated as being asettable cementitious composition and in FIGURES l and 2 it will beunderstood that it is desired to rapidly determine the presence andposition of the upper surface 46 of a plug formed thereby andaccordingly it will be understood that in FIGURES 1 and 2 the plugmaterial 44 has at best only attained a very initial set of relativelylow load bearing strength. Were it not for the relatively great totalsurface bearing area of the plate 32 the determination of the presenceand position of the upper surface 46 of the plug material 44 could notgenerally be determined inasmuch as a pipe string not provided wlth thedevice 10 would sink downwardly within the relatively unconsolidatedplug material 44 to such an extent that the presence of the plugmaterial 44 could not be verified or alternatively a substantial amountof time would have to be lost in permitting the plug material 44 to setto its final rigidity to enable/verifying the presence (if) the plugwith a pipe string not provided with the tool The foregoing is conidered as illustrative only of the principles of the invention. Further,since numerous modifications and changes will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation shown and described, and accordinglyall suitable modifications and equivalents may be resorted to, fallingwithin the scope of the invention as claimed.

What is claimed as new is as follows:

1. A method of determining the presence and position of anunconsolidated plug established by a settable cementitious plug-formingmaterial in a generally restricted diameter bore hole of a well prior tosignificant consolidation of the settable plug-forming material, whereinthe bore hole is filled with at least a two phase column of liquidcomprising at least an upper relatively nonviscous circulating liquidphase and a lower relatively viscous phase comprising the settableplug-forming material, which method comprises the steps of making up andlowering into the well a pipe string having means on the lower endthereof of a diameter lesser than the diameter of the bore hole andcapable of supporting the weight of the pipe string on theunconsolidated plug while maintaining circulation of the relativelynonviscous phase of the liquid column in the bore hole, and verifyingthe presence of and position of the unconsolidated plug by cessation ofdownward movement of the pipe string.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 7/ 1952 Germany.

DAVID H. BROWN, Primary Examiner U.S. C1.X.R.

